The invention is directed toward a multiplex circuit arrangement, particularly for the actuation of load stations in motor vehicles. More particularly, the invention relates to such a multiplex circuit arrangement wherein each station includes a hardware processor for the rapid serial exchange of data and a driver circuit, with the multiplex circuit arrangement comprising a bus system operating with an active level and a passive level, and with the individual stations being connected via a network structure, e.g. a star structure.
A circuit arrangement of this type is disclosed, for example, in DE 3,730,468.A1. This circuit arrangement has a star-shaped structure, with the actual star point, however, extending practically over the length of the entire vehicle. This results in a significant drawback because damage to the central data line may lead to the total malfunction of the system. The large local expanse of the star point has also been recognized as a problem in this publication. Another drawback of the prior art arrangement is that a large amount of circuitry is required for the individual stations. Each station requires control devices including microprocessors and appropriate software, data converters, data processors and bus transfer members, with the function of these subscriber stations ultimately being only to realize decoupling of the individual interface units.
DE 3,149,142.A1 discloses a circuit arrangement having a relatively complicated central station that is equipped with two computers. This circuit arrangement operates according to the master-slave principle, which is also its primary drawback. Modern arrangements do not operate with a central electronic unit, but with equivalent interconnected groups (multi-master principle). Moreover, in this prior art each sub-group is star-shaped and is approached over a separate line which is a drawback since in the automobile art it must be assumed that a plurality of sub-groups will exist, for example, for the four doors, the four corners of the vehicle, the air-conditioning system, the seat adjustment, the sunroof, at various locations in the engine compartment, at the center console, etc. According to the prior art system, no two such sub-groups must be connected to the same data line if their mutual decoupling is to be ensured. If data must be exchanged between two sub-groups, this can be effected only by way of an intermediate stop in the central unit, for example, for the transmission of operator actuated keys in the region of the rear seats in order to operate a door window.
Based on this, it is the object of the invention to configure a circuit arrangement of the above-mentioned type in such a way that the load lines are distributed in a favorable manner and can be secured by way of a central fuse box, with the central region being locally limited if the circuit is realized in a star structure. Moreover, it should be possible to provide coupling to any existing data line by way of a network without incurring decoupling losses. Each station should be able to communicate with every other station without switching processes and without data transfer by way of a microprocessor, with the data of highest priority being transmitted in each case. Finally, it should also be possible to add further subscriber stations to the network without affecting the remaining system, with addresses being assigned to each individual station.